Based on recent preliminary data, it is proposed that inhibitors of TIP60 acetyltransferase will be useful as modulators of a cell's DNA damage response and as sensitizers to chemo- or radiotherapy. The acetyltransferase activity can be measured in vitro with TIP60 complex isolated from cells and with bacterially produced recombinant TIP60. Aim 1 will develop an in vitro assay for TIP60 activity and optimize it for use in 96-well plates for a high throughput screen for TIP60 inhibitors. Aim 2 will demonstrate the utility of the screen to identify a known (relatively non-specific) inhibitor of TIP60. This inhibitor will be taken through the secondary screens that will test the effect of the inhibitor on a cell's response to DNA damage, on cell survival after DNA damage and on the acetyltransferase activity of the cell's TIP60 complex. Together these aims will establish a high throughput assay of TIP60 inhibitors and demonstrate the readiness of the assay for a high throughput screen for chemical inhibitors. The primary high throughput screen and the biological secondary screens established will help screen for chemicals that are biologically active for inhibiting TIP60 in cells. Because TIP60 is involved in the DNA damage response the inhibitors are expected to be useful as sensitizers to chemo- or radio-therapy. In addition, because TIP60 regulates the transcriptional program of many cancer related proteins like the androgen receptor, p53 and Myc, the TIP60 inhibitors could function as specific inhibitors of oncogenic or stress-induced pathways. [unreadable] [unreadable] [unreadable]